The majority of automatic machines used in the packaging industry normally comprise an electronic control unit for controlling operation of the automatic machine. The electronic control unit comprises an electronic card, mounted on which is a programmable controller, for example a PLC (programmable-logic controller) device, configured for running a program for controlling the automatic machine. The electronic card comprises a memory module for storing the control program. The most modern electronic cards can be interfaced with external computers, for example an appropriately programmed personal computer, via one or more communication ports, for example serial communication ports.
Whenever it is desired to replace the program for controlling the automatic machine, for example with an updated version of the control program or else with a totally new control program, the memory module is replaced with a new memory module containing the new or updated control program, or else, more commonly, the new control program is installed directly in the memory module by means of an external computer interfaced with the electronic card by means of the communication port. It is expedient for the re-programming of the automatic machine to be performed by specialized staff with a good knowledge of the logic of operation of the automatic machine, typically technicians authorized by the producer of the automatic machine. It frequently happens, instead, that re-programming is performed by the end user, who frequently is not fully aware, at least as are, instead, authorized technicians, of the detailed operation of the automatic machine, and hence could re-program the automatic machine in an erroneous way, thus increasing the risk of consequent malfunctioning or breakdown of the automatic machine that is difficult to identify even by authorized technicians. In addition, when the end user is re-programming the automatic machine non having sufficient acquaintance with it, he could involuntarily change some fundamental characteristics of the program, such as the general logic of operation and/or the overall time of execution of the program to an extent such as to render the automatic machine and/or the control unit no longer compliant with the guarantee, or even worse, such as to render the automatic machine no longer safe for the operator and/or no longer able to provide a product in conformance with requirements of safety for the consumer.
Consequently, in order to understand whether the malfunctioning has a hardware origin (the automatic machine in itself) or a software origin (programming of the control device), authorized technicians frequently first replace the electronic card with a new one: if the machine continues to function badly, then the failure is on the machine; otherwise, it means that the malfunctioning was caused by the control program, the origin of which, i.e., who has installed it and when, is frequently not known.
PLC devices used for controlling automatic machines are normally of a modular type; namely, they comprise at least one processing module, which comprises the processor and the memory on which the control program can be installed, and a plurality of additional modules, for example, digital or analog input/output modules governed by the processing module for acquiring field signals and for driving the various electromechanical actuators of the automatic machine, communication modules, and complementary processing modules. This modular structure presents the following advantages: it can be expanded at will by adding processing modules or input/output modules according to the requirements of the automatic machine and enables easy maintenance in so far as the modules can be replaced individually in the event of failure. The ease of replacement of a module can constitute, however, a risk for reliability for the automatic machine. In fact, the end user of the automatic machine, or in general unauthorized staff, could easily replace an original module with another module having characteristics that do not meet the requirements of design and operation of the automatic machine to an extent such as to render the automatic machine and/or the control unit no longer compliant with the guarantee, or even worse, such as to render the automatic machine no longer safe for the operator and/or no longer able to provide a product compliant with requirements of safety for the consumer.